Damper regulator



March 3, 1953 E. R. RACK ErAL 2,630,272

DAMPER REGULATOR SToKa.

N i g INVENToRs 2 g gq EDWARD R. RACK I BY RoeER-r J. DUNCAN N a a m ,n JOHN T. DULAK tf o t u m 2'/ March 3, 1953 E. R. RACK ErAL DAMPER REGULATOR 4 Sheets-Sheet 2 Filed Sept. 16. 1949 F/ca. 3

INVENToRs F. 4 EDwARb R. RACK /G-v. BY ROBERT J. DuncAn OHN T. DULAK uw ATToANeY March 3, 1953 E. R. RACK ET A1. 2,630,272

DAMPER REGULATOR Filed Sept. 16. 1949 4 Sheets-Sheet 5 (CLoseo) Flc-1. /O

F' G- 9 INVENToRs EDWARD R. RACK BY Rosen-r J. DUNCAN Jol-m T. DuL K ATTORNEY Patented Mar. 3, 1953 DAMPER REGULATOR Edward R. Rack, Robert J. Duncan, and John T.

Dulak, Milwaukee, Wis., assignors to A P Controls Corporation, a corporation of Wisconsin Application September 16, 1949, Serial No. 116,132

4 Claims.

This invention relates generally to a device for regulating the check and draft dampers on coal fired heating plants.

Damper regulators are generally under control of a thermostat. When there is no demand for heat the furnace is checked-the check is open and the draft door is closed. When the thermostat calls for heat an electric circuit including a motor is completed to move the dampers to the firing position with the check closed and the draft open. The firing position is maintained until the thermostat is satisfied.

Some regulators stall the motor in the iiring position while others stop the motor in the firing pasition. The stalled motor type both overheats and hunts. The motor coil winding eventually deteriorates due to overheating. The hunting means that the true firing condition is not maintained. Those regulators which stop the motor in the firing position do not fail safe without additional mechanism complicating the installation.

An object of this invention is to provide a regulator which maintains the firing position without hunting.

Another object is to provide a regulator which fails safe.

A further object is to provide a regulator having a motor which runs cool, thus increasing motor life.

Still another object is to provide a damper regulator powered by a motor which neither stalls nor :stops in the ring position.

A still further object is to provide a safe, efficient damper regulator which operates smoothly and quietly.

Another object is to provide a motor operated ydamper regulator which will not reduire oiling.

Damper regulators are preferably provided with a basement or Stoke switch which may be manually operated to move the doors to firing position so the furnace may be stoked without smoke pouring into the basement. The Stoke switch is preferably of the type which automatically trips out after a predetermined time interval to restore the regulator to thermostatic control. The basement switch may be tripped manually, cut the automatic feature provides a safety factor.

Another object of this invention is to provide a simple basement switch which may be manually set and automatically or manually tripped out.

A further object is to provide a damper regulator stoke switch which is ,held closed by a bimetallio latch which warps to open the switch after a predetermined time interval regardless of the ambient temperature.

This regulator is additionally provided with a limit switch which eliminates danger of overheating. The limit switch may be responsive to air or water temperature or steam pressure. In the event the furnace is of the forced draft type a lblower switch is provided to close the fan circuit to increase the draft.

Objects and advantages other than those above set forth will be apparent from the following description when read 'in connection with the accompanying drawing in which:

Figs. l and 2 are side and front elevations, respectively, of the regulator;

Fig. 3 is a plan view of the lower portion of the regulator;

Figs. 4, 5 and 6 are sections respectively taken on lines 4 4, 5 5 and 6 6 in Fig. 3;

Fig. 7 is a fragmentary view similar to Fig. 6 but showing another relationship of the parts in the operation cycle;

Fig. 8 is a section taken on line 8 8 in Fig. 2;

Fig. 9 shows the Stoke switch closed;

Fig. 10 is a view taken as indicated by line l0 |0 in Fig. 9;

Fig. 11 is a schematic drawing of the hydraulic system;

Fig. 12 is a combined wiring diagram and schematic drawing of the regulator; and

Fig. 13 is a fragmentary view which, in conjunction with Fig. 1, illustrates the operation of the blower switch.

Referring to the drawings in detail, the regulator is provide-d with casing Ii! having bushings I 2, M for shaft I6 carrying damper arm I8 at the side of the casing. The so-called damper arm has diametrically opposed arms 20, 22 which are adapted to be connected to the check and draft dampers by means of suitable chain or cable reeved in pulleys. Heavily tensioned spring 24 is hooked into bushing I4 and the damper arm iiange 26 within the cupped back-side of damper arm I8. The arm is biased to the checked position shown in Figs. 1 through 3 by spring 24 and is adapted to be rotated through approximately in the direction indicated yby the arrow in Fig. 1 when motor 28 is energized. The motor is on the secondary or low voltage side of transformer 30 (Fig. 12) mounted on the left hand (Fig. 2) side of bracket 32 which is carried on casing cover plate 34 and secured to casing I 0. Thus the transformer would appear in the background of Fig. 1 but has been omitted to clarify the showing of the other parts. Thermostat 36 (Fig. 12) is connected into the secondary of transformer 30 in series with low voltage motor 20.

When the thermostat closes and calls for heat, motor 25.3 is energized to drive gear pump 33 through spring coupling d which eliminates possible binding due to any misalignment of the shafts. Since the casing is filled with oil to the indicated level (below shaft l0 to eliminate leakage problems), the gear pump will deliver oil under pressure through conduit l2 to the underside of Valve di! in well 416 through the small hole iii at the bottom of the well. As may be seen in Figs. 5, 6 and '7, valve i4 is biased to its lowermost position by means of spring 50 seated within the valve at one end and against seat 52 held in well d0 by means of pin 54. Seat 52 ts loosely within the well to allow for passage of oil around its periphery for a reason which will appear hereinafter.

The oil delivered under pressure from gear pump 3d to the underside of Valve 44 will raise the valve against the force of spring 50 until small opening 56 in the side of the well is exposed to allow oil to flow into the bottom of cylinder 5t through conduit 60. The oil acts against the underside of piston 62 to lift the piston and impart rotational movement to damper arm shaft it through connecting rod Sli and crank B which is secured to the shaft by means of screws 68 and l0.

Piston 62 will be raised by the oil pressure until the piston abuts depending cylinder flange l2. At this point the pressure would normally tend to increase until electric motor 28 driving gear pump 38 stalled. However, means are provided for bleeding a small amount of oil from the delivery side of the gear pump to prevent stalling the motor and encountering the consequent hunting effect. Thus the lower end of valve 44 is threaded to provide a small capillary passage from the underside of the valve to annular groove in the Valve. Groove 'M communicates with the hollow upper portion of the valve through diametrical holes it. Therefore, when piston 62 has reached its upper limit, the oil pressure builds up and forces valve it up against the spring force until it strikes pin 5d or until the spring force equals the pressure. Oil bleeds past the threaded tip of Valve ifi into groove 1Q, through hole l5, and out of the top of well 00 back into the casing. Since but a small amount of oil can bleed past the valve tip, the pressure on the outlet side of the gear pump is held at a high value which imposes an additional load on the motor thus tending to slow it down, but the motor will in no event stall. Therefore, piston 62 is held in its upper position without hunting. The damper arm has been rotated through approximately 90 to open the draft and close the check.

When the thermostat is satisfied, the motor circuit is broken. The high pressure oil in the cylinder ES immediately tends to bleed through the gear pump to relieve the pressure. When the pressure has dropped a small amount, the force of spring 50 is sufficient to move valve M down to the bottom of well 40 thus cutting oi communication between cylinder 58 and the gear pump. It will be noted, however, that groove l'Li now communicates directly with hole 5S and conduit @0 (Fig. 7). Since the force of damper arm spring 2e acts on piston 52, the oil in cylinder 53 ows rapidly out through apertures 'I6 in valve it and up through the hollow stem. to

4 spill over the top of well 46 to return the damper doors to the check position.

It will be apparent that the size of the oil passages and the depth of the threads on the valve tip may be varied to obtain the most desirable operating characteristics. The control is smooth and silent in operation and holds the doors in the ring position without any hunting eiect. Should the current be interrupted, the device fails safe since it has the same eifect as the thermostat opening.

The stoke switch is mounted on vertical terminal board i8 carried by bracket 32. The switching elements comprise three parallel resilient leaves 79, 80, 8| which are separated from each other by insulating blocks 82 and mounted on bracket 84. The outer extremities of switch elements i0, 80, 8| carry contacts which are normally separated (Fig. 2). Manual control knob 00 is positioned immediately adjacent the switch elements. Headed stop member 88 is positioned adjacent knob 86 to serve a two-fold function. The head overlies ilange 90 xed on knob 05 to limit outward movement of the knob in response to the force of compressed spring 92. Projections 94, B6 on control knob St are adapted to strike the shaft of stop 88 to limit rotational movement of knob 86. In addition to biasing the knob outwardly, spring 92 also tends to rotate the knob to the position shown in Fig. 2 where projection 04 abuts the shafts of stop 83. When stoke switch B is rotated counterclockwise (Fig. 2) cam surface 9B carried thereby acts against switch elements 19, 80, 0| to push the switch contacts together against the inherent resiliency of the elements (Fig. 9). At this time bimetallic latch |00 drops about its pivot |02 to engage the end of cam surface 98 and hold the stoke switch in the closed position (Fig. 9).

As may be seen in Fig. 12 rotation of the stoke switch to bring the switch contacts together shunts out the thermostat and causes current flow through two parallel circuits. One of these circuits includes heater |04 strapped under conductor |05 which is carried on shaft |02 with bimetallic latch |00. The heater branch may optionally include an indicator light |08 which serves as a warning when the basement switch has been closed. The other branch of the parallel circuit causes current ow through motor 23 to drive gear pump 38 and rotate damper arm IS to move the check and draft doors to the firing position. The furnace may now be stoked without smoke pouring into the basement.

The heat from heater |04 is conducted to bimetallic latch |00 through conductor |06. This causes the latch to warp and after a predetermined time interval to disengage cam 9S on the stoke switch and permit spring 92 to rotate the switch back to its normal position and interrupt current flow through the parallel circuits. This restores the regulator to its normal condition under control of thermostat 36. However, the stoke switch may be manually returned to its normal position by pressing in against the force of spring 92 until switch cam 90 operates against up-turned corner l |0 of the bimetallic latch and cams the latch upwardly as spring 92 rotates the knob. After switch cam 98 is disengaged from latch |00, spring 92 pushes the knob outwardly to return it to its normal position ready for another operation.

When the latch is in its normal position (Fig. 2) it rests on the top of stoke switch cam 98.

When the switch has been closed (Fig. 9) calibrating screw ||2 in the depending portion of conductor |06 abuts against compensating bimetal ||4 mounted on bracket 32. The compensating bimetal responds to ambient temperature to provide a variable datum and compensate for any time deviations caused by ambient temperature changes. Therefore, the heater may be designed to automatically open the Stoke switch after a predetermined time interval which will not vary with ambient temperature changes. Since the heat is conducted to the bimetallic latch, the interval can be held within very close limits.

The limit control comprises bulb H6 which is subjected to the temperature of the medium which is to be the limiting factor. A temperature increase will cause a corresponding pressure increase in the bulb which acts on snap diaphragm I0 to push pin |20 against shoulder |22 to move contact |24, in opposition to compression force of spring |25, away from contact |26 and break the high voltage circuit on the primary of the transformer. This, of course, interrupts current flow to the motor and permits the damper arm to rotate back to the checked position.

The response temperature of the limit control is regulated by varying the compression of spring |23. Manual control knob |30 is rotatably mounted on screw threading on the end of diaphragm pin |20 and provides a seat for spring |28 which also seats against the vertical portion of bracket 32. Thus as knob |30 is rotated, it moves in or out of the screw threading to increase or decrease the compression of spring |20 which tends to aid the diaphragm pressure. As knob |30 is rotated counter-clockwise from the position shown in Fig. 2, it moves outwardly to decrease the spring compression and therefore increase the response temperature of the limit control.

If the furnace is provided with a forced draft, the circuit to the blower cannot close until the doors are substantially in the firing position. Damper arm flange 26 is extended in one portion to provide cam surface |32 (Figs. 2 and 3). Follower |34 is xed on the end of pin |36 rotatably mounted in bushings |38 secured to bracket 32. When damper arm I8 is in its normal position, cam |32 holds follower |34 in a position shown in Fig. l. In this position cam |40 on shaft |36 bears against flat face |42 of blower switch element |44 to hold contact |46 from stationary contact |48 on conductor |50 (which also carries the high voltage contact |26 of the limit control). As damper arm I8 moves to the ring position when the thermostat calls for heat or the basement switch is closed, cam |32 holds the follower in position to keep the blower switch open until the damper arm has substantially reached the ring position. At this point (Fig. 13) cam |32 on the damper arm terminates permitting the follower to drop down and rotate cam |40 on shaft |36 away from switch element |44 to permit the inherent resiliency of the element to move contact |46 against the stationary contact |48 to complete the circuit to the blower. As soon as the damper arm starts the return movement to the checked position, follower |34 will be moved to break the blowei` circuit.

Operation Considering first the normal operation under thermostatic control, it will be noted that closure of thermostat 36 energizes motor 28 to drive gear pump 38 and deliver oil to the underside of valve 44. Valve 44 is raised to expose port 56 in valve Well 46 and permit oil to ow into cylinder 56 to lift piston 62 and rotate the damper arm to the firing position. When piston 62 has reached the limit of its upward movement, the pressure on the outlet side of the gear pump increases and exerts an additional load on the motor thus slowing the motor. The threaded tip on valve 44 permits a small amount of oil to bleed back into the oil reservoir by flowing through groove '|'4 and hole 'I6 into the hollow interior of the valve and out over the top of well 46. The capillary passage determined by the cooperation of the threaded valve tip and the wall of the well is designed to permit sucient bleed to prevent stalling the motor while maintaining the pressure on the underside'of piston 62 to hold the doors in the ring position.

When the thermostat is satisfied, the motor circuit is broken and for a short time oil will tend to flow back through gear pump 38. As soon as the pressure in the system is decreased a small amount, spring 50 returns valve 44 to its lower position (Fig. 7) where groove 'I4 communicates with port 56 to permit oil to flow rapidly from cylinder 58 out through the interior of the valve and over the top of well 46 as spring 24 within the damper arm forces piston 62 to its lower position. Thus the return -to the checked position is more rapid than would be possible if the oil had to ow out through gear pump 38.

Basement switch 86, when rotated from its normal posi-tion (Fig. 2) to the closed position (Fig. 9), brings the contacts carried by leaf-like switch elements T0, 80, 8| together to shunt out the thermostat while establishing two parallel circuits. The stoke switch is held in the closed position by means of bimetallic latch |00. One branch of the parallel circuit causes current flow through heater |04 and light bulb |08, while the other branch causes current flow through motor 28 to drive gear pump 38 and move the damper arm to the firing position as described above. While the stoke switch is closed, heat is conducted from heater |04 to bimetallic latch 00 by conductor |06. After a predetermined time interval, latch |00 warps upwardly out of contact with switch cam 98 to permit spring 92 to rotate the switch back to its normal position and restore the regulator to thermostatic control. Bimetal ||4 compensates for ambient temperature changes so that the action of heater |04 on bimetallic latch |00 is not affected by ambient changes, thereby insuring consistent time intervals on the automatic trip-out of the stoke switch.

The stoke switch may be manually tripped by pressing knob 86 inwardly until switch cam 03 operates against latch cam l0 to raise the latch and permit spring 92 to rotate the switch clockwise and to push the switch back out to its normal position ready for another operation.

Temperature variations felt by bulb ||6 are resolved into pressure variations acting on diaphragm ||3 which snaps outwardly, when the limiting temperature has been exceeded, to open contacts |24, |26 and break the primary circuit of the transformer. Rotation of limit control knob |30 varies the response temperature by changing the compression of spring |28 which tends to aid the diaphragm pressure.

Cam surface |32 is provided on the damper arm to hold the follower |34 in the position illustrated in Fig. 1 until Ithe damper arm has rotated to the ring position to permit follower |34 to drop down as shown in Fig. 13. When the damper arm is in the checked position, cam |40 on shaft |36 carrying follower |34 operates against flat M2 on resilient switch element its to hold contact |156 from stationary contact |48 on the primary side of the transformer. However, when follower |31?l drops down (Fig. 13) cam Idil moves away from flat H12 to allow the inherent resiliency of switch element It@ to bring contact Mii against contact IBS and close the circuit to the blower.

Since the regulator motor must run continuously to maintain the `firing condition against the bias tending to return the dampers to the checked position, the ring condition is held without the hunting characteristic of the stalled motor type regulator and the regulator fails safe without requiring extra devices complicating the structure. It is to be noted that the stoke switch is designed to maintain the time interval allowed for stoking constant in spite of ambient temperature variations and without the use of a clock device. The motor bushings require no attention since they are immersed in oil. Similarly, the wear of other moving parts in the oil is reduced to a minimum. It will be apparent that this regulator may be modied in many ways without departing from the spirit of the invention. With this in mind the scope is to be determined only by the scope of the claims.

We claim:

i. A furnace damper regulator comprising, in combination, a damper actuator adapted for connection to the check and draft dampers of a i'urnace and being movable between a normal position in which the dampers check the nre and another position in which the dempers are in ring position, means biasing said actuator to said normal position, a cylinder, a piston in said cylinder and connected to said actuator, said piston being `in a rst position when said actuator is in said normal position and being in a second position when said actuator is in said other position, an electric moto-r, a liquid supply, a pump connected to said motor, conduit means connecting the outlet of said pump toy said cylinder, valve means in said conduit means, a thermostat, an electric circuit including said motor and said thermostat, closure of said thermostat in response to heat demand being operative to energize said motor until the thermostat opens, said valve means being responsive to the pressure increase occasioned by operation of said pump to permit liquid to flow into said cylinder to move said piston to said second position, and means for bleeding oil from the delivery side of said pump to prevent the hydraulic pressure from increasing to the point where said motor stalls when said piston is in said second position and said actuator is in said other position, said valve means being responsive to the hydraulic pressure decrease incident to de-energization or said motor to vent 4said cylinder and permit liquid to flow rapidly from the cylinder as said piston and said actuator respectively return to said iirst and normal positions under influence of said biasing means.

2. A furnace damper regulator comprising, in combination, a damper actuator adapted for connection to the check and draft dampers of a furnace and being movable between a normal position in which the dampers check the re and another position in which the dampers are in ring position, means biasing said actuator to said normal position, and' electric motor, hy-

draulic means operatively connecting-said motor and said actuator, a thermostat, an electric circuit including said motor and said thermostat, closure of said thermostat in response to heat demand being operative to energize said motor until the thermostat opens, said motor moving .said actuator to said other position when energized, another circuit including said motor, normally open switch means operable to complete said other circuit when closed to energize said motor and move the actuator to said other position to permit stoking, bimetallic means for latching said switch means 'in closed position, said other circuit including a heater which is heated upon closure of said switch means, means for conducting heat from said heater to said bimetallic latch means to warp said latch after an interval of time, and means for bleeding liquid from said hydraulic means to prevent said motor from stalling when said actuator is in said other position.

3. A furnace damp-er regulator comprising, in combination, a. damper actuator adapted for connection to the check and draft dampers of a :Cui-nace and being movable between a normal position in which the dampers check the re and another position in which the dampers are in firing position, means biasing said actuator to said normal position, anelectric motor, hydraulic means operatively connecting said motor and said actuator, a thermostat, an electric circuit including said motor and said thermostat, closure of said thermostat in response to heat demand being operative to energize said motor until the thermostat opens, said motor moving said actuator to said other position when energized, another circuit including said motor, normally open switch means operable to complete said other circuit when closed to energize said motor and move the actuator to said other position to permit stoking, bimetallic means for latching said switch means in closed position, said other circuit including a heater which is heated upon closure of said switch means, means for conducting heat from said heater to said bimetallic latch means to warp said latch after an interval of time, and means compensating said bimetallic latch means for ambient temperature to maintain said interval constant, and means for bleeding liquid from said hydraulic means to prevent said motor from stalling when said actuator is in said other position.

e. The combination with an electrically operated damp-er regulator adapted to control the check and draft dempers of a furnace for increased or decreased heat delivery, of a thermostat for controlling actuation of said regulator in accordance with heat demand of the medium heated by the furnace, of a panel, a plurality of normally separated resilient switch elements mounted on said panel and operable when moved into contact with each other to cause said regulator to increase the heat delivery from the furnace independently of said thermostat, a manually operable knob mounted on said panel for movement between iirst and second positions, a spring biasing said knob to said i'irst position, a cam on said knob and operable to move said switch elements into contact with each other upon movement of said knob to said second position, a bimetallic latch engageable lwith said cam when said knob is in said second position to hold the knob in said second position, said latch being adapted to warp out of engagement with said cam when heated to permit said spring to return REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Kronmiller Sept. 12, 1933 Schaefer July 31, 1934 Persons Nov. 12, 1935 Day Aug. 6, 1940 Hilmer Dec. 31, 1940 Newton Jan. 6, 1942 Carlson July 28, 1942 Baak Aug. 4, 1942 White Jan. 19, 1943 Millerwise July 11, 1944 Hilmer et al Dec. 10, 1946 

